Radiation therapy apparatus

ABSTRACT

A radiation therapy apparatus has a multi-leaf collimator device having a pair of collimator components which respectively comprise a plurality of leaves arranged close to one another such that the leaves face one another across an irradiation axis, and configured to set a desired irradiation field by individually moving the leaves. One of the collimator components is arranged with an offset with respect to the other collimator component, within a range of a leaf-width.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a radiation therapy apparatus used fora therapy of diseases such as malignant tumors, and particularly to theradiation therapy apparatus including a multi-leaf collimator devicewhich allows an extent of an object that is exposed to radiation (whichwill be referred to as an “irradiation field” hereafter) to be set withhigh precision.

2. Description of the Related Art

From the perspective of radiation protection, the radiation therapyapparatus includes a collimator device formed of a material the natureof which renders it impermeable to radiation such as tungsten or thelike, thereby allowing the exposure to radiation to be limited to atherapy part including a body. Such a collimator device needs to have afunction of carefully forming the irradiation field that approximates ashape of the therapy part without a formation of a penumbra.Accordingly, such a collimator device has a first collimator and asecond collimator arranged in the irradiation direction such that theyoverlap.

With such an arrangement, the first collimator provided on a near sideof a radiation source is configured in a form of a single unitcomprising a pair of members disposed such that they face each otheracross an irradiation axis. Such an arrangement allows that the membersdrive so as to adjust a distance therebetween. For example, the membersdrive along an arc-shaped path around the radiation source as a center.On the other hand, the second collimator provided on a far side of theradiation source is configured in the form of a pair of collimatorcomponents (blocks) such that the collimator components face each otheracross the irradiation axis in an orthogonal direction to a movingdirection of the first collimator. Each of the collimator components ofthe second collimator has multiple leaves arranged close to one another,which can be individually moved so as to adjust a distance therebetweenalong the arc-shaped path around the radiation source as the center.

The second collimator is the so-called multi-leaf collimator devicecomprising a pair of collimator components 1A and 1B arrangedsymmetrically, as shown in FIG. 8, for example. The collimator component1A has tens of leaves 1A1-1An arranged close to one another. Thecollimator component 1B has tens of leaves 1B1-1Bn arranged close to oneanother. The leaves 1A1-1An and the leaves 1B1-1Bn can be adjustedindividually along the arc-shaped path. Such an arrangement allows theseleaves to be driven individually along the arc-shaped pat by respectivedriving devices each of which is provided to the corresponding leaf.Such an arrangement allows the first collimator comprising thecollimator components facing each other to be moved in an X direction soas to adjust the distance therebetween. In addition, such an arrangementallows the leaves 1A1-1An and the leaves 1B1-1Bn facing one another tobe moved individually in a Y direction so as to adjust the distancetherebetween. Such a combination of adjustment operations provides aformation of an irradiation field “U” in a desired shape thatapproximates the shape of the therapy part. Such an arrangement allowsthe leaves facing one another to be moved along the arc-shaped path,thereby providing irradiation without the formation of the penumbra inthe irradiation field “U”.

It is extremely important for the radiation therapy apparatus toirradiate only the therapy part which is approximately equal to a focuswithout exposing a healthy tissue to radiation. From this point of view,the multi-leaf collimator provides an extremely important function.However, the focus develops in various shapes. This leads to difficultyin providing the irradiation field “U” that matches the shape of such afocus. In order to solve this problem, examples of conceivablearrangements include an arrangement in which the collimator components1A and 1B include the leaves 1A1-1An and 1B1-1Bn, respectively, whichare a minute pitch. Such an arrangement requires as many leaves A1-1Anand 1B1-1Bn as possible, by narrowing a leaf-width.

However, such an arrangement having an increased number of leaves, whichprovides the minute pitch, requires leaves with a reduced theleaf-width. Even with ordinary arrangements, the leaves are formed withthe leaf-width of around 2 to 3 [mm]. An arrangement having leaves witha narrower width than those of ordinary leaves has problems in themanufacturing process due to warped leaves etc., examples of whichinclude difficulty in manufacturing the collimator with a desired levelof precision.

In addition, these leaves must be moved individually so as to providethe desired irradiation field. Such an arrangement requires respectivedriving device. This leads to difficulty in designing a layout of asupporting mechanism and a driving mechanism, which allow such a greatnumber of leaves arranged closely adjacent to one another to beindividually moved, and the layout of a detection mechanism fordetecting a movement of each leaf. Furthermore, in order to preventradiation leaks from gaps between the adjacent leaves, there is a needto arrange the leaves with as small the gap as possible between theadjacent leaves, e.g., with the gap of around 0.05 to 0.1 [mm]. However,it is extremely difficult to provide such high-precision manufacturingand fabrication in order to realize such a design.

In view of such a situation, an arrangement has been proposed in whichthe second collimator is provided in a form of two separate stagesarranged with a predetermined interval along an irradiation direction.With such an arrangement, the leaves are arranged with an offset betweenan upper-stage collimator and a lower-stage collimator such that eachboundary between the adjacent leaves including upper-stage collimatorcomponents respectively does not match any of the boundaries between theadjacent leaves of the lower-stage collimator components respectively(see “Japanese Patent Publication (Laid-open: KOKAI) No. 2002-210026”,for example). With such an arrangement, although the leaves are formedwith the same leaf-width as those of the ordinary arrangements, such anarrangement provides the same effect as that provided by an arrangementhaving leaves formed with half the leaf-width of those of the ordinaryarrangements. This is able to make the irradiation field further minute.Such an arrangement allows the shape of the irradiation field to beadjusted with higher precision such that it approximates the therapypart, thereby protecting the healthy tissue from being exposed toradiation.

Such a technique disclosed in the aforementioned Japanese Patentpublication can eliminate to a certain extent the problem of anarrangement having an increased number of leaves formed with a reducedleaf-width. However, such a technique provides an arrangement in whichthe second collimator is provided in the form of two separate stagesarranged with an interval in the irradiation direction. Accordingly, thenumber of components required for the supporting mechanism and thedriving mechanism, which allow the leaves to be individually moved, andthe number of components required for the detection mechanism fordetecting the movement of each leaf, are twice those of the ordinaryarrangements. This leads to a complicated configuration and alarger-sized collimator device, which are new problems. Such alarger-sized collimator leads to reduction in a space for the therapy,which is a problem of the radiation therapy apparatus itself.

SUMMARY OF THE INVENTION

The present invention has been made in order to solve the aforementionedproblems. Accordingly, it is an object thereof to provide the radiationtherapy apparatus including the multi-leaf collimator device having afunction of adjusting the irradiation field with high resolution suchthat it approximates the shape of the therapy part using the secondcollimator provided in the form of a single stage, i.e., not in the formof two stages, without increasing the number of leaves.

To solve the above-described problems, the present invention providesthe radiation therapy apparatus, comprising: A radiation therapyapparatus comprising: a multi-leaf collimator device having a pair ofcollimator components which respectively comprise a plurality of leavesarranged close to one another such that the leaves face one anotheracross an irradiation axis, and configured to set a desired irradiationfield by individually moving the leaves, wherein one of the collimatorcomponents is arranged with an offset with respect to the othercollimator component, within a range of a leaf-width.

To solve the above-described problems, the present invention providesthe radiation therapy apparatus, comprising: a multi-leaf collimatordevice having a pair of collimator components which respectivelycomprise a plurality of leaves arranged close to one another such thatthe leaves face one another across an irradiation axis, and configuredto set a desired irradiation field by individually moving the leaves,wherein at least one of the collimator components is configured suchthat it can be relatively moved with respect to the other collimatorcomponent, within a range of a leaf-width.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIG. 1 is an external view which shows a usage condition of theradiation therapy apparatus according to a present embodiment;

FIG. 2 is a side view which shows a driving direction of the firstcollimator included the collimator device in the present embodiment;

FIG. 3 is a side view which shows a first example of a driving directionof the second collimator provided to the collimator device in thepresent embodiment;

FIG. 4 is a side view which shows a second example of a drivingdirection of the second collimator provided to the collimator device inthe present embodiment;

FIG. 5 is a top view which shows a constitution example of the secondcollimator provided to the collimator device in the present embodiment;

FIG. 6 is a top view which shows the irradiation field example of thesecond collimator in the present embodiment;

FIG. 7 is a top view which shows an arrangement example and a formationof the irradiation field by arranging the leaves included the secondcollimator in the present embodiment; and

FIG. 8 is a top view which shows the arrangement and the formation ofthe irradiation field by arranging the leaves included the secondcollimator in the related art.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Detailed description will be made with reference to FIG. 1 through FIG.7 regarding a radiation therapy apparatus including a multi-leafcollimator device according to an embodiment of the present invention.It should be noted that, in these drawings, the same components aredenoted by the same reference numerals.

FIG. 1 is an external view which shows a usage condition of theradiation therapy apparatus according to a present embodiment. First,description will be made in a schematic fashion with reference to FIG. 1regarding a configuration of the radiation therapy apparatus accordingto the present embodiment.

In broad terms, the radiation therapy apparatus has an irradiationdevice 10 which uses a radiation source to irradiate a predetermineddirection, a therapy table 20 on which an object (a person who needs atherapy) P, including a focus, lies and which sets a positioning of atherapy part to be irradiated, and a control device 30 which organicallycontrols a components of the radiation therapy apparatus, e.g., theirradiation device 10 and the therapy table 20.

The irradiation device 10 includes a fixed frame 11 installed on afloor, a turnable frame 12 which is turnably supported by the fixedframe 11, an irradiation head 13 provided to a tip portion extending inthe horizontal direction from one end of the turnable frame 12, and acollimator device 14 which is a built-in component of the irradiationhead 13. With such an arrangement, the turnable frame 12 can be turnedwith respect to the fixed frame 11 over approximately 360 degrees arounda rotation center axis “H” extending in the horizontal direction.Furthermore, the collimator device 14 is provided such that it can beturned with respect to the irradiation head 13 around an irradiationaxis “I”. It should be noted that the intersection of a rotation centeraxis “H” for the turnable frame 12 and the irradiation axis “I” will bereferred to as the “isocenter (IC)” hereafter. With such an arrangement,the turnable frame 12 is configured such that it can be turned accordingto various kinds of irradiation, examples of which include a rotationirradiation, a pendulum irradiation, an intermittent irradiation, etc.

Furthermore, the therapy table 20 is installed on the floor such that itcan be turned over a predetermined angle range in a direction of arrow“G” along an arc with the isocenter IC as a center. Furthermore, atable-top 22, on which the object P can lie, is provided to a top of thetherapy table 20. Here, the table-top plate 22 is supported by an upperportion mechanism 21. The upper portion mechanism 21 includes amechanism which allows the table-top 22 to be moved in a longitudinaldirection indicated by an arrow “e” and a lateral direction indicated byan arrow “f”.

Furthermore, the upper portion mechanism 21 is supported by an elevatormechanism 23. The elevator mechanism 23 has a link mechanism, forexample. Such an arrangement allows the elevator mechanism 23 itself tobe moved in a vertical direction indicated by an arrow “d”, therebyallowing the upper portion mechanism 21 and the table-top 22 to be movedin a predetermined range in the vertical direction. Moreover, theelevator mechanism 23 is supported by a lower portion mechanism 24. Thelower portion mechanism includes a mechanism which allows the elevatormechanism 23 to be turned in the direction indicated by an arrow “F”,with the position that is distant from the isocenter IC by a distance“L” as the center. Such an arrangement allows the upper portionmechanism 21 and the table-top 22 to be turned in a predetermined rangeof angle in the direction indicated by the arrow “F”, in addition to theelevator mechanism 23.

It should be noted that such an arrangement allows a medical staff “D”such as a surgeon or the like to operate an operation unit provided tothe control device 30, thereby setting the positioning of the object Pand adjusting the collimator device 14 which defines an irradiationfield at a radiation therapy.

It is important for the radiation therapy to irradiate only the therapypart in a concentrated manner without damaging a normal tissue. Thecollimator device 14 controls a position to be irradiated, whichprotects the normal tissue from being exposed to radiation. With such anarrangement, the collimator device 14 is provided in the form of abuilt-in component of the irradiation head 13 such that it can be turnedaround the irradiation axis “I”.

Next, description will be made regarding the collimator device 14 withreference to FIG. 2 through FIG. 7. FIG. 2 is a side view which showsthe driving direction of the first collimator provided to the collimatordevice 14. FIG. 3 is a side view which shows a first example of adriving direction of the second collimator provided to the collimatordevice 14. FIG. 4 is a side view which shows a second example of adriving direction of the second collimator provided to the collimatordevice 14. It should be noted that FIG. 3 and FIG. 4 show the collimatordevice 14 viewed in an orthogonal direction orthogonal to the directionin which the collimator 14 shown in FIG. 2 is viewed. Furthermore, ahousing of the collimator device 14 is not shown in these drawings. FIG.5 is a top view which shows a constitution example of the secondcollimator provided to the collimator device 14 in the presentembodiment.

As shown in FIG. 2 through FIG. 4, in general, the collimator device 14has two kinds of collimators (a first collimator 140 and a secondcollimator 141) formed of a heavy metal such as tungsten or the like.These two kinds of collimators are arranged along the irradiationdirection from the radiation source “S” such that they overlap. Withsuch an arrangement, each of the collimators 140 and 141 has a pair ofseparate components arranged such that they face each other (see thecomponents denoted by reference numerals 140A, 140B, 141A, and 141B inFIG. 2 and FIG. 3). Here, such a pair of components forming thecollimator 140 or 141 is differentiated by reference symbols “A” and “B”for convenience of understanding.

With such an arrangement, each of the first collimator component 140Aand the second collimator component 140B provided on a near side of theradiation source “S” is configured in the form of a single unit, asclearly shown in FIG. 2. Furthermore, the collimator components 140A and140B are arranged such that an end face of the collimator component 140Aand an end face of the collimator component 140B face each other acrossthe irradiation axis “I”. Such an arrangement allows the collimatorelements 140A and 140B to be moved in a direction of an arrow “X” alongan arc-shaped path around the radiation source “S” as a center bydriving devices 142A and 142B, thereby adjusting a distance between thecollimator components 140A and 140B.

Also, the second collimator components 141A and 141B provided on a farside of the radiation source “S” can be moved along the arc-shaped path,as clearly shown in FIG. 3. Furthermore, the collimator components 141Aand 141B are arranged such that an end face of the collimator component141A and an end face of the collimator component 141B face each otheracross the irradiation axis “I”. Such an arrangement allows thecollimator elements 141A and 141B to be moved by driving devices 143Aand 143B in the orthogonal direction to the aforementioned arrangingdirection of the collimator elements 140A and 140B, i.e., in a directionof an arrow “Y” along the arc-shaped path around the radiation source“S” as the center, thereby adjusting a distance between the collimatorcomponents 141A and 141B.

In another example shown in FIG. 4, the second collimator components141A and 141B are arranged such that the end face of the collimatorcomponent 141A and the end face of the collimator component 141B faceeach other across the irradiation axis “I”. Such an arrangement allowsthe collimator elements 141A and 141B to be moved by the driving devices143A and 143B in the orthogonal direction to an arranging direction ofthe first collimator elements 140A and 140B, i.e., in the direction ofthe arrow “Y” along a straight path, thereby adjusting the distancebetween the collimator components 141A and 141B.

Note that description will be made below regarding an arrangement whichallows the first collimator 140 to be driven in the driving direction“X” as described with reference to FIG. 2, and which allows the secondcollimator 141 to be driven in the driving direction “Y” as describedwith reference to FIG. 3.

As shown in FIG. 2, the second collimator component 141A (141B) hasmultiple leaves 141A1-141An (141B1-141Bn) arranged close to one another.FIG. 5 shows the detailed configuration thereof.

That is to say, driving devices 143A1-143An (143B1-143Bn) are providedto the respective leaves 141A1-141An (141B1-141Bn) forming the secondcollimator component 141A (141B). Such an arrangement allows the leaves141A1-141n (141B1-141Bn) to be driven individually in the direction ofthe arrow “Y” along the arc-shaped path around the radiation source “S”as the center, thereby adjusting the distances therebetween.

Such an arrangement allows the leaves 141A1-141An of the secondcollimator component 141A and the leaves 141B1-141Bn of the secondcollimator component 141B to be moved individually in the “Y” directionso as to adjust the distance therebetween, in addition to allowing thefirst collimator components 140A and 140B to be moved in the “X”direction so as to adjust the distance therebetween. The combination ofthese operations allows the irradiation field “U” to be formed in adesired shape such that it approximates the shape of the therapy part“T” which is approximately equal to the focus.

In ordinary arrangements, the second collimator components 141A and 141Bare configured in a left-right symmetrical manner. Furthermore, withsuch ordinary arrangements, the leaves 141A1-141An and the correspondingleaves 141B1-141Bn are arranged at fixed positions such that they faceone another without any offset. That is to say, with ordinary secondcollimator, the leaves 141A1-141An and the corresponding leaves141B1-141Bn are arranged at fixed positions such that they face oneanother without any offset, as described with reference to FIG. 8.

On the other hand, the present invention according to the presentembodiment provides an arrangement in which the collimator component141A having the leaves 141A1-141An and the collimator component 141Bhaving the leaves 141B1-141Bn are arranged at fixed positions such thatthe end faces of the leaves 141A1-141An and the end faces of the leaves141B1-141Bn face one another with an offset which is a predeterminedvalue within the range of a leaf-width “W”, as shown in FIG. 7. FIG. 7is an enlarged view of the leaf portion shown in FIG. 5, and shows anarrangement in which the collimator component 141B, which is onecomponent of the second collimator, and the collimator component 141A,which is the other component of the second collimator, are arranged withan offset in the same direction of half the leaf-width “W”.

In FIG. 7, the leaves 141B1-141Bn of the one collimator component 141Bare indicated by bold lines for convenience of understanding. With suchan arrangement shown in FIG. 7, the leaves 141B1-141Bn and the leaves141A1-141An the opposite collimator component 141A are arranged suchthat the end faces thereof face each other with an offset of “W/2”. FIG.7 shows an arrangement in which the collimator component 141B isarranged with such an offset by shifting the collimator component 141Btoward the leaf 141An, as indicated by an arrow “R”. Also, anarrangement may be made in which the collimator component 141B isarranged with an offset by shifting the collimator component 141B towardthe leaf 141A1, i.e., in the direction opposite to that indicated by thearrow “R”.

Such an arrangement allows the shape of the irradiation field “U” to beadjusted with a minute resolution that corresponds to half theleaf-width “W”. However, an arrangement in which the one collimatorcomponent 141B is arranged with an offset with respect to the othercollimator component 141A in a simple manner changes a part of the areathat shields the exposure to radiation into an area through which thetherapy part is exposed to radiation. Accordingly, the positions of theend faces of the leaves 141B1-141Bn facing the collimator component 141Ashould be adjusted such that the irradiation field that includes such anew area through which the therapy part is exposed to radiationapproximates the desired irradiation field.

Description has been made regarding an arrangement in which all theleaves 141A1-141An of the second collimator component 141A and theleaves 141B1-141Bn of the second collimator component 141B are formedwith the same leaf-width “W”. However, the leaves 141A1 and 141An (141B1and 141Bn), which are positioned at the end of the second collimatorcomponent 141A (141B), are preferably formed with a larger leaf-widththan those of the other leaves positioned on the inner side thereof. Thereason is that such an arrangement prevents the formation of a gap at anedge of the irradiation field “U” provided by an arrangement in which atleast one of the second collimator components 141A and 141B is arrangedwith an offset with respect to the other.

The present invention is not restricted to the above-describedembodiment, rather, various embodiments may be made. For example, therange of the offset between the one collimator and the other collimatorcan be set to a desired value within the range of the leaf-width “W”.

Also, an arrangement may be made including a mechanism which adjusts theoffset between the one collimator component 141B and the othercollimator component 141A within the range of the leaf-width “W”,instead of an arrangement in which the one collimator and the othercollimator are arranged with a fixed offset in the leaf-width direction.Such an arrangement provides a minute adjustment of the irradiationfield “U”, thereby providing the irradiation field “U” approximating thedesired shape with high resolution. That is to say, in order to adjustthe irradiation field “U” described with reference to FIG. 2 and FIG. 3,such an arrangement has a function of adjusting at least one of thepositions of the second collimator components 141A and 141B to a certainextent in the orthogonal direction to the moving direction in which thedistances between the leaves 141A1-141An and 141B1-141Bn are adjusted(i.e., the X direction in which the distance between the firstcollimator components 140A and 140B is adjusted).

In order to adjust the positions of the second collimator components141A and 141B in such a manner, such an arrangement employs a similarmechanism to that for the first collimator components 140A and 140B,which allows at least one of the second collimator components 141A and141B to be moved in the direction of the arrow “X” along the arc-shapedpath around the radiation source “S” as the center. Alternatively, anarrangement may be made in which a lead screw provided to each secondcollimator component is driven by a motor. With such an arrangement, themovement of the second collimator component is detected by an encoder, apotentiometer, or the like, thereby allowing the position of the secondcollimator component to be detected and adjusted in a simple manner. Itshould be noted that, when both the second collimator components 141Aand 141B are moved along the direction of the arrow “X”, the secondcollimator components 141A and 141 b are moved in directions opposite toone another (i.e., the direction of the arrow “R” shown in FIG. 7 andthe direction opposite thereto). Furthermore, with such an arrangement,the second collimator components 141A and 141B, which face one another,are moved along the arc-shaped path around the radiation source “S” asthe center. This eliminates the problem of a penumbra in the irradiationfield “U”.

As described above in detail, without employing a multi-leaf collimatorhaving a two-stage configuration, the present embodiment provides theirradiation field “U” with approximately the same minute resolution asthat provided by an arrangement employing the multi-leaf collimatorhaving a single-stage configuration including an increased number ofleaves. That is to say, such an arrangement allows the irradiation field“U” to be formed in a simple manner such that it approximates, withhigher precision, the shape of the therapy part, which can develop invarious shapes. With such an arrangement, the irradiation field “U” thusformed is exposed to radiation. This allows only the site of thedisease, which is to be treated, to be irradiated while protecting thehealthy tissue from being exposed to radiation.

Also, an arrangement may be made having an additional function ofadjusting, with the minute resolution, at least the positions of thesecond collimator components 141A and 141B. Such an arrangement allowsthe shape of the irradiation field “U” to be adjusted such that itapproximates a desired shape with higher precision. Thus, such anarrangement protects the object from unnecessary exposure to radiation,thereby improving the safety of the therapy. Furthermore, such anarrangement does not involve a large-size multi-leaf collimator device,thereby eliminating the problem of occupying a large part of a space forthe therapy. Thus, the present invention provides an extremely usefulradiation therapy apparatus.

1. A radiation therapy apparatus comprising: a multi-leaf collimatordevice including a pair of collimator components on a same plane, eachcollimator component including a plurality of leaves, one collimatorcomponent of the pair of collimator components and an other collimatorcomponent of the pair being arranged close to one another such that thecollimator components face one another across an irradiation axis andset a desired irradiation field by individually moving the leaves,wherein leaves of the one collimator component are arranged with anoffset with respect to leaves of the other collimator component along adirection in which the leaves of the one collimator component arearranged, within a range of a leaf-width.
 2. A radiation therapyapparatus according to claim 1, wherein the leaves are movableindividually along an arc-shaped path around a radiation source as acenter.
 3. A radiation therapy apparatus according to claim 2, whereinthe leaves are arranged orthogonally to a moving direction of the leavesalong the arc-shaped path.
 4. A radiation therapy apparatus according toclaim 1, wherein the offset with which the collimator components arearranged is approximately half the leaf-width.
 5. A radiation therapyapparatus, comprising: a multi-leaf collimator device including a pairof collimator components on a same plane, each collimator componentincluding a plurality of leaves, one collimator component of the pair ofcollimator components and an other collimator component of the pairbeing arranged close to one another such that the collimator componentsface one another across an irradiation axis and set a desiredirradiation field by individually moving the leaves, wherein the onecollimator component is movable with respect to the other collimatorcomponent along a direction in which the leaves of the one collimatorcomponent are arranged.
 6. A radiation therapy apparatus according toclaim 5, wherein the leaves are movable individually along an arc-shapedpath around a radiation source as a center.
 7. A radiation therapyapparatus according to claim 6, wherein the leaves are movable andarranged orthogonally to a moving direction of the leaves along thearc-shaped path.
 8. A radiation therapy apparatus according to claim 5,wherein at least one of the collimator components is movable in a rangeof approximately half the leaf-width.